Fishery-induced selection on an Alpine whitefish: quantifying genetic and environmental effects on individual growth rate

Size-selective fishing, environmental changes and reproductive strategies are expected to affect life-history traits such as the individual growth rate. The relative contribution of these factors is not clear, particularly whether size-selective fishing can have a substantial impact on the genetics and hence on the evolution of individual growth rates in wild populations. We analysed a 25-year monitoring survey of an isolated population of the Alpine whitefish Coregonus palaea. We determined the selection differentials on growth rate, the actual change of growth rate over time and indicators of reproductive strategies that may potentially change over time. The selection differential can be reliably estimated in our study population because almost all the fish are harvested within their first years of life, i.e. few fish escape fishing mortality. We found a marked decline in average adult growth rate over the 25 years and a significant selection differential for adult growth, but no evidence for any linear change in reproductive strategies over time. Assuming that the heritability of growth in this whitefish corresponds to what was found in other salmonids, about a third of the observed decline in growth rate would be linked to fishery-induced evolution. Size-selective fishing seems to affect substantially the genetics of individual growth in our study population.

Analysis of variables that are not directly observable: influence on decision-making during the research process

The sample dimension, types of variables, format used for measurement, and construction of instruments to collect valid and reliable data must be considered during the research process. In the social and health sciences, and more specifically in nursing, data-collection instruments are usually composed of latent variables or variables that cannot be directly observed. Such facts emphasize the importance of deciding how to measure study variables (using an ordinal scale or a Likert or Likert-type scale). Psychometric scales are examples of instruments that are affected by the type of variables that comprise them, which could cause problems with measurement and statistical analysis (parametric tests versus non-parametric tests). Hence, investigators using these variables must rely on suppositions based on simulation studies or recommendations based on scientific evidence in order to make the best decisions.

Draft environmental report on Cape Verde

Faced with recurrent drought and famine during five centuries of human occupation, the small and densely populated Cape Verde Islands have a history of severe environmental problems. The arid climate and steep, rocky terrain provide scant resources for traditional subsistance farming under the best conditions, and in years of low rainfall the failure of rainfed crops causes massive food shortages. Agricultural use of steep slopes where rainfall is highest has led to soil erosion, as has removal of the island's vegetation for fuel and livestock. Pressure on the vegetation is particularly severe in dry years. International aid can provide relief from famine, and the introduction of modern agricultural and conservation techniques can improve the land and increase yield, but it is unlikely that Cape Verde can ever be entirely self -sufficient in food. Ultimately, the solution of Cape Verde's economic and environmental problems will probably require the development of productive urban jobs so the population can shift away from the intensive and destructive use of land for subsistance farming. In the meantime, the people of Cape Verde can best be served by instituting fundamental measures to conserve and restore the land so that it can be used to its fullest potential. The primary environmental problems in Cape Verde today are: 1. Soil degradation. Encouraged by brief but heavy rains and steep slopes, soil erosion is made worse by lack of vegetation. Soils are also low in organic matter due to the practice of completely removing crop plants and natural vegetation for food, fuel or livestock feed. 2. Water shortage. Brief and erratic rainfall in combination with rapid runoff makes surface water scarce and difficult to use. Groundwater supplies can be better developed but capabilities are poorly known and the complex nature of the geological substrate makes estimation difficult. Water is the critical limiting factor to the agricultural capability of the islands. 3. Fuel shortage. Demand for fuel is intense and has resulted in the virtual elimination of native vegetation. Fuelwood supplies are becoming more and more scarce and costly. Development of managed fuelwood plantations and alternate energy sources is required. 4. Inappropriate land use. Much of the land now used for raising crops or livestock is too steep or too arid for these purposes, causing erosion and destruction of vegetation. Improving yield in more appropriate areas and encouraging less damaging uses of the remaining marginal lands can help to alleviate this problem.

Experiments on substratum roughness, grainsize and volume influence on the motion and spreading of rock avalanches

The main objective of the research is to link granular physics with the modelling of rock avalanches. Laboratory experiments consist to find a convenient granular material, i.e. grainsize and physical behaviour, and testing it on simple slope geometry. When the appropriate sliding material is selected, we attempted to model the debris avalanche and the spreading on a slope with different substratum to understand the relationship between the volume and the reach angle, i.e. angle of the line joining the top of the scar and the end of the deposit. For a better understanding of the mass spreading, the deposits are scanned with a laser scanner. Datasets are compared to see how the grain size and volume influence a debris avalanche. The relationship between the roughness and grainsize of the substratum shows that the spreading of the sliding mass is increased when the roughness of the substratum starts to be equivalent or greater than the grainsize of the flowing mass. The runout distance displays a more complex relationship, because a long runout distance implies that grains are less spread. This means that if the substratum is too rough the distance diminishes, as well if it is too smooth because the effect on the apparent friction decreases. Up to now our findings do not permit to validate any previous model (Melosh, 1987; Bagnold 1956).

Genetic and environmental effects on the covariation betweencolour polymorphism and a life history trait

Variation in coloration with a strong underlying genetic basis is frequently found within animal populations but little is known about its function. Covariation between colour polymorphism and life-history traits can arise because morphs perform differently among environments or because they possess alternative alleles coding for key life-history traits. To test these two hypotheses, we studied a population of tawny owls Strix aluco, a bird displaying red, brown and grey morphs. We assessed the colour morph of breeding females, swapped eggs or hatchlings between pairs of nests, and examined how body condition in 3-week-old nestlings covaries with coloration of foster and genetic mothers. Redder foster and genetic mothers produced young in better condition. Because in two other years we observed that greyish females produced offspring in better condition than those of red females, the present study suggests that colour polymorphism signals genetic and phenotypic adaptations to cope with a fluctuating environment.

Impact of biological and environmental variabilities on biological monitoring: an approach using toxicokinetic models

Biological monitoring of occupational exposure is characterized by important variability, due both to variability in the environment and to biological differences between workers. A quantitative description and understanding of this variability is important for a dependable application of biological monitoring. This work describes this variability,using a toxicokinetic model, for a large range of chemicals for which reference biological reference values exist. A toxicokinetic compartmental model describing both the parent compound and its metabolites was used. For each chemical, compartments were given physiological meaning. Models were elaborated based on physiological, physicochemical, and biochemical data when available, and on half-lives and central compartment concentrations when not available. Fourteen chemicals were studied (arsenic, cadmium, carbon monoxide, chromium, cobalt, ethylbenzene, ethyleneglycol monomethylether, fluorides, lead, mercury, methyl isobutyl ketone, penthachlorophenol, phenol, and toluene), representing 20 biological indicators. Occupational exposures were simulated using Monte Carlo techniques with realistic distributions of both individual physiological parameters and exposure conditions. Resulting biological indicator levels were then analyzed to identify the contribution of environmental and biological variability to total variability. Comparison of predicted biological indicator levels with biological exposure limits showed a high correlation with the model for 19 out of 20 indicators. Variability associated with changes in exposure levels (GSD of 1.5 and 2.0) is shown to be mainly influenced by the kinetics of the biological indicator. Thus, with regard to variability, we can conclude that, for the 14 chemicals modeled, biological monitoring would be preferable to air monitoring. For short half-lives (less than 7 hr), this is very similar to the environmental variability. However, for longer half-lives, estimated variability decreased. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: tables detailing the CBTK models for all 14 chemicals and the symbol nomenclature that was used.] [Authors]

Liming influence on soil chemical properties, nutritional status and yield of alfalfa grown in acid soil

Alfalfa is an important forage crop with high nutritive value, although highly susceptible to soil acidity. Liming is one of the most efficient and prevailing practices to correct soil acidity and improve alfalfa yield. The objective of this study was to evaluate response to liming of alfalfa grown in a greenhouse on a Typic Quartzipsamment soil. The treatments consisted of four lime rates (0, 3.8, 6.6 and 10.3 Mg ha-1) and two cuts. Alfalfa dry matter increased quadratically with increasing lime rates. In general, dry matter yield was maximized by a lime rate of 8.0 Mg ha-1. Except for the control, the dry matter nutrient contents in the treatments were adequate. The positive linear correlation between root and nodule dry matter with lime rates indicated improvement of these plant traits with decreasing soil acidity. The soil acidity indices pH, base saturation, Ca2+ concentration, Mg2+ concentration, and H + Al were relevant factors in the assessment of alfalfa yield. The magnitude of influence of these soil acidity indices on yield as determined by the coefficient of determination (R²) varied and decreased in the order: base saturation, H + Al, pH, Ca and Mg concentrations. Optimum values of selected soil chemical properties were defined for maximum shoot dry matter; these values can serve as a guideline for alfalfa liming to improve the yield of this forage on acid soils.